sync-upstream-branches: turn the workflow into a matrix

The workflow still only handles the `git-gui` branches, but is now
almost generic enough to become a matrix workflow that also handles the
`gitster/git` synchronization.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/sync-upstream-branches.yml

@@ -1,31 +1,37 @@
-name: sync-git-gui-branches
+name: sync-upstream-branches
 
 on:
   schedule:
     - cron: '31 22 * * *'
   workflow_dispatch:
 
-env:
-  SOURCE_REPOSITORY: j6t/git-gui
-  TARGET_REPOSITORY: gitgitgadget/git
-  TARGET_REF_NAMESPACE: git-gui/
-
 # We want to limit queuing to a single workflow run i.e. if there is already
 # an active workflow run and a queued one, queue another one canceling the
 # already queued one.
 concurrency:
   group: ${{ github.workflow }}
 
 jobs:
-  sync-git-gui-branches:
+  sync-upstream-branches:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        spec:
+          - source-repo: j6t/git-gui
+            target-repo: gitgitgadget/git
+            target-ref-namespace: git-gui/
+
     steps:
       - name: check which refs need to be synchronized
         uses: actions/github-script@v7
         id: check
         with:
           script: |
-            const [targetRepoOwner, targetRepoName] = process.env.TARGET_REPOSITORY.split('/')
+            const sourceRepo = ${{ toJSON(matrix.spec.source-repo) }}
+            const targetRepo = ${{ toJSON(matrix.spec.target-repo) }}
+            const targetRefNamespace = ${{ toJSON(matrix.spec.target-ref-namespace) }}
+
+            const [targetRepoOwner, targetRepoName] = targetRepo.split('/')
             core.setOutput('target-repo-owner', targetRepoOwner)
             core.setOutput('target-repo-name', targetRepoName)
 
@@ -72,10 +78,10 @@ jobs:
               }
             }
 
-            const sourceRefs = await getRefs(process.env.SOURCE_REPOSITORY)
-            const targetRefs = await getRefs(process.env.TARGET_REPOSITORY, process.env.TARGET_REF_NAMESPACE)
+            const sourceRefs = await getRefs(sourceRepo)
+            const targetRefs = await getRefs(targetRepo, targetRefNamespace)
 
-            const targetPrefix = `refs/heads/${process.env.TARGET_REF_NAMESPACE}`
+            const targetPrefix = targetRefNamespace ? `refs/heads/${targetRefNamespace}` : 'refs/heads/'
 
             const refspecs = []
             const toFetch = new Set()
@@ -138,7 +144,7 @@ jobs:
           set -ex
           git init --bare
 
-          git remote add source "${{ github.server_url }}/$SOURCE_REPOSITORY"
+          git remote add source '${{ github.server_url }}/${{ matrix.spec.source-repo }}'
           # pretend to be a partial clone
           git config remote.source.promisor true
           git config remote.source.partialCloneFilter blob:none
@@ -151,4 +157,4 @@ jobs:
           # push the commits
           printf '%s' '${{ steps.check.outputs.refspec }}' |
           xargs -d ' ' -r git -c http.extraHeader='${{ steps.auth.outputs.header }}' \
-            push "${{ github.server_url }}/$TARGET_REPOSITORY"
+            push '${{ github.server_url }}/${{ matrix.spec.target-repo }}'